The publication of the correspondence of TS Eliot is one of the more formidable literary undertakings of our time. The first volume – devoted to letters the poet wrote between the ages of 10, as a boy in St Louis, Missouri, and 34, when he was settled in London and had just brought out the defining poem of his era, The Waste Land – appeared a decade ago. Since then, every year or two, another selection, each one near a thousand pages, has arrived. Twenty such books are planned. We have reached number eight, which takes in the correspondence that Eliot wrote immediately before the war, between 1936 and 1938.

The task of editing and glossing and footnoting has been (since the death of Eliot’s widow, Valerie, in 2012) the indefatigable work of John Haffenden. His pace of production, 7,600 pages in 10 years, is impressive. The only comparable effort, the processing of the complete correspondence of Bertrand Russell, Eliot’s erstwhile friend and the secret lover of his first wife, Vivienne Haigh-Wood, has long submerged a batallion of editors at McMaster University in Canada, with no end in sight.

So what is the experience of combing through the business memos and notes of encouragement to literary hopefuls that the poet wrote as he approached the age of 50? In some ways it is like eavesdropping on the most maddening of confessionals: just as the poet seems about to mine some inner anxiety, he digresses into bland thank you notes and exhaustive letters to the Church Times on the proceedings of the Anglican synod.

In one letter he is “frothing and fuming” over a proposal by John Masefield for poetry readings in pubs

Eliot had built a life as a one-man publishing industry. In these three years he both laid the ground for the Four Quartets with visits to Little Gidding and East Coker and further indulged the playfulness of Old Possum’s Book of Practical Cats. He was a full-time director at Faber & Faber, still editor of the Criterion quarterly (jobs that earned him £500 a year) and now a celebrated playwright; Murder in the Cathedral had opened in 1935, and was bringing him a steady £5 a week in royalties. He was too, as these pages attest, emphatically and literally, a man of letters.

Typically, Eliot began 1936 in a New Year’s resolution frame of mind with eight letters on 1 January alone. One was in the form of a cat poem in reply to a party invitation from his goddaughter, Alison Tandy: “Mr Possum wishes that his name was Tristram Shandy… so he could reply in poetry to the kind invitation of Miss Alison Tandy…” Another, an overdue letter of seven pages to his older brother, Henry, begins with thanks for his gift of a silk dressing gown, and continues with reproaches to his brother for having raised long-standing fraternal grievances.

Eliot, it appears, stands accused of affectation years earlier. He attempts to excuse his perceived behaviour with reference to his torturous marriage to the increasingly disturbed Vivienne, “suffering from a feeling of guilt at having married a woman I detested and consequently feeling that I must put up with anything”.

Eliot with Virginia Woolf, centre, and his first wife, Vivienne. Photograph: CSU Archv/Everett / Rex Features

In Haffenden’s previous volume he included diary entries of Vivienne’s for the first time. These entries revealed the extremes of “Viv’s” stalker-like delusion years after Eliot had finally left her and instructed his friends to conceal his whereabouts. She is mostly absent even from footnotes by 1936, but still shadows the poet. In July 1936 Eliot writes to Dorothy Pound, wife of Ezra: “I am rather shaky at the moment,” he confesses. “I ran into my late wife in Wigmore Street an hour ago and had to take to my heels: only people who have been ‘wanted’ know the sort of life I lead...”

This volume closes with the decision, which Eliot had long avoided, to have Vivienne committed to an asylum. The final crisis is described in a desperate letter from Maurice Haigh-Wood, Vivienne’s brother: “V. was found wandering the streets at 5 o’clock this morning…” he tells Eliot. “She [later] asked me if it was true that you had been beheaded…” Eliot sends the papers to have her committed to a psychiatric hospital in Stoke Newington, north London, where she died in 1947.

Those traumas hardly appear to impinge on Eliot’s working life, however. The bulk of his letters concern the fastidious business of publishing. There are letters to Henry Miller about the difficulties of producing Anaïs Nin’s explicit diaries on financial grounds. Lawrence Durrell, then unpublished, also faced rejection. “Another 10 years growing up, and working away with the language and literary form, would help,” Eliot wrote.

At the same time Eliot is beset by anxiety about his own Old Possum poems (“Nobody wants to make a fool of himself when he might be better employed”), and occasionally splutters outrage at the drift of modernity. In one letter he is “frothing and fuming” over a proposal by John Masefield for poetry readings in the back rooms of pubs. “The English Verse Speaking Association,” Eliot notes, “is a monstrous cancer in this Land, stretching now its foul tentacles toward the public house.”

What is perhaps most striking in all these pages, though, is what is not there. In years that we view as a preface to the great rupture in modern history, hardly a hint registers in Eliot’s correspondence. There is an abrupt note to Vanessa Bell to offer condolences for the death of her son Julian, killed by a bomb blast in the Spanish civil war. This precedes anguished exchanges with Bell’s sister, Virginia Woolf, about how he can politely reject a posthumous collection of Julian’s essays. Eliot excuses his prevarication with a publisher’s familiar embarrassment. He had been unable to write sooner, he says, because of “a gorse spine festering in my thumb”.

Eliot turned 50 in September 1938. The following day is notable, in the context of these 1,100 pages, because it contains the single mention, by name, of a figure who will loom large over the next volume. “One still doesn’t know,” Eliot writes to an American acquaintance, “whether Hitler will pipe down in the face of so much opposition from so many sides, or not…”

• The Letters of TS Eliot Volume 8: 1936-1938, edited by Valerie Eliot and John Haffenden, is published by Faber (£50). To order a copy go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £15, online orders only. Phone orders min p&p of £1.99